This invention relates to a switch which is actuated when it senses a rate of descent which exceeds a set amount.
The switch of the instant invention is used to detect when the device to which it is attached is descending vertically at or above a set rate. An example of where a vertical descent rate detector switch can be employed is in an emergency brake control system for an aircraft passenger loading bridge. The distal end of such a bridge is raised or lowered in order to properly position a cab at the end of the bridge with respect to the door of an aircraft. If, in the event of an emergency, the distal end of the bridge descends too rapidly, the brake control system applies a brake on the bridge drive mechanism to slow the descent of the bridge. The rate detector switch of the instant invention actuates the control system to apply the brake when it senses a rate of descent of the bridge in excess of a set amount.
When attempting to use a commercially available switch in the brake control system of a passenger loading bridge, it was found that the switch was actuated and the brake applied when the bridge was moved horizontally as well as when it was moved vertically. This adversely affected the ability of an operator to move the bridge horizontally to engage an aircraft. Consequently, it was necessary to develop a switch which detected and was actuated when it sensed a vertical rate of descent which equalled or exceeded a set amount but was relatively insensitive to horizontal forces. It was also necessary to make a switch which did not require an external power supply or other circuitry.